Experimental and theoretical investigation of the reaction between CO$_{2}$ and carbon dioxide binding organic liquids

Abstract

The reaction kinetics of CO 2 absorption into new carbon dioxide binding organic liquids (CO 2 BOLs) was comprehensively studied to evaluate their potential for CO 2 removal. A stopped-flow apparatus with conductivity detection was used to determine the CO 2 absorption kinetics of novel CO 2 BOLs composed of DBN (1,.0]non-5ene)/1-propanol and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene)/1-butanol. A modified termolecular reaction mechanism for the reaction of CO 2 with CO 2 BOLs was used to calculate the observed pseudo-first-order rate constant k 0 (s −1 ) and second-order reaction rate constant k 2 (m 3 /kmol.s). Experiments were performed by varying organic base (DBN or TBD) weight percentage in alcohol medium for a temperature range of 288-308 K. It was found that k 0 increased with increasing amine concentration and temperature. By comparing using two different CO 2 BOL systems, it was observed that the TBD/1-butanol system has faster reaction kinetics than the DBN/1-propanol system. Finally, experimental and theoretical activation energies of these CO 2 BOL systems were obtained and compared. Quantum chemical calculations using spin restricted B3LYP and MP2 methods were utilized to reveal the structural and energetic details of the single-step termolecular reaction mechanism.

Theoretical investigation of carbon dioxide capture by aqueous boric acid solution: A termolecular reaction mechanism

“…As a continuation to our studies on the CO 2 capture [18][19][20]27], in which CO 2 was captured by different amine-alcohol mixtures through a single step termolecular mechanism as explained above [18][19][20] and also CO 2 was trapped between the amorphous form or crystalline ice slab of the water and methylamine [27], an alternative single step termolecular reaction mechanism among carbon dioxide, boric acid and water is suggested in the current study, and the methodology used and results obtained are given in the following sections.…”

“…A similar termolecular reaction mechanism which was previously suggested in our studies for similar carbon dioxide capturing systems [18][19][20] can be adapted to current reaction system which contains boric acid, carbon dioxide and water. different concentrations are also used in the carbon dioxide capture [21][22][23][24][25].…”

“…Other than amine based solvent and alcohol mixtures, aqueous potassium carbonate and boric acid mixtures at the B3LYP/6-31G(d) level of theory [28][29][30][31][32]. This level calculations yielded well results in our previously performed similar reaction mechanism studies [18][19][20]. After obtaining the most stable isolated structures of the boric acid, CO 2 and water molecules, reactant and product systems for the interaction of these molecules according to the termolecular reaction mechanism are prepared.…”

“…Recently, in our combined experimental and theoretical studies, we followed the single step termolecular reaction mechanism for the capture of carbon dioxide by 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN)/1-propanol and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD)/1butanol mixtures [18], DBN/1-hexanol, TBD/1-hexanol and 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG)/ 1-hexanol mixtures [19], and BTMG/1-propanol mixture [20]. Our findings in these combined experimental and theoretical studies [18,19,20] were in good agreement and our results suggested that the reaction among carbon dioxide, amine based organic solvent and alcohol takes place very likely according to the single step termolecular mechanism. Other than amine based solvent and alcohol mixtures, aqueous potassium carbonate and boric acid mixtures at the B3LYP/6-31G(d) level of theory [28][29][30][31][32].…”

Innovative Carbon Dioxide‐Capturing Organic Solvent: Reaction Mechanism and Kinetics

“…Thus, during regeneration CO 2 is separated and the solvent switches to the less polar nonionic form by modest heating . In addition, CO 2 COSs have certain tunable properties; for instance, changing the alcohol type can affect the reaction rate to some extent . On the other hand, it is probable to achieve a significant effect by adding groups to an amidine or guanidine molecule.…”